Abstract : This is a reference guide for JOSS users to (1) the language used for couching instructions to JOSS; (2) JOSS's responses to instructions; (3) the collection of machine-language routines (in JOSS's central computer) responsible for interpreting and responding to instructions; and (4) the details and decisions that bilaterally influenced the language and the design and implementation of the routines. The myriad details of total system design are given constant exposure, and particular emphasis is placed on the delicate balance and symbiosis that must exist among system, language, computer, and routines and on the pervasive effects of each component on the others. The material is presented in a narrative form, augmented by flow-chart representations of most of the principal routines, and is in part designed to serve as prolegomena to the annotated machine-language listings of the routines (copies of which are obtainable from RAND). (Author)